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##Pyth, 17 bytes

>lQC.e.>bkC+_PtQQ

Explanation:

                      implicit: Q=input
>                     First
  l Q                   len(Q) elements of the
  C .e                  Transpose of enumerated map lambda b,k:
       .>                 Rotate the kth element rightwards by
          b
          k               k.
       C +              Transpose of: Q concatenated to
           _ P t Q        itself reversed without first and last elements.
           Q

Try it here.

Pyth, 17 bytes

>lQC.e.>bkC+_PtQQ

Explanation:

                      implicit: Q=input
>                     First
  l Q                   len(Q) elements of the
  C .e                  Transpose of enumerated map lambda b,k:
       .>                 Rotate the kth element rightwards by
          b
          k               k.
       C +              Transpose of: Q concatenated to
           _ P t Q        itself reversed without first and last elements.
           Q

Try it here.

##Pyth, 17 bytes

>lQC.e.>bkC+_PtQQ

Explanation:

                      implicit: Q=input
>                     First
  l Q                   len(Q) elements of
  C .e                  the transpose of mapped enumerate
       .>                 rotate the kth element right by
          b
          k               k
       C +              over transpose of: Q concatenated to
           _ P t Q        itself reversed without first and last elements
           Q

Try it here.

##Pyth, 17 bytes

>lQC.e.>bkC+_PtQQ

Explanation:

                      implicit: Q=input
>                     First
  l Q                   len(Q) elements of the
  C .e                  Transpose of enumerated map lambda b,k:
       .>                 Rotate the kth element rightwards by
          b
          k               k.
       C +              Transpose of: Q concatenated to
           _ P t Q        itself reversed without first and last elements.
           Q

Try it here.

##Pyth, 17 bytes

>lQC.e.>bkC+_PtQQ

Explanation:

                      implicit: Q=input
>                     First
  l Q                   len(Q) elements of
  C .e                  the transpose of mapped enumerate
       .>                 rotate the kth element right by
          b
          k               k
       C +              over Q concatenated to
           _ P t Q        itself reversed without first and last elements
           Q

Try it here.

##Pyth, 17 bytes

>lQC.e.>bkC+_PtQQ

Explanation:

                      implicit: Q=input
>                     First
  l Q                   len(Q) elements of
  C .e                  the transpose of mapped enumerate
       .>                 rotate the kth element right by
          b
          k               k
       C +              over transpose of: Q concatenated to
           _ P t Q        itself reversed without first and last elements
           Q

Try it here.